The Spectra and Classification of L and T Dwarfs

In this contribution, I discuss some of the salient features of L and T dwarf spectra in both the red optical (6300–10000 {\AA}) and near-infrared (1–2.5 $\text{micron}$) wavelength regimes. Important absorption bands and lines, including those of H${}_2$O, CH${}_4$, FeH, CrH, CO, and the alkali metal lines, are identified, and the development of recent classification schemes based on these features are discussed. I briefly point out future work required in these wavelength regions and in the mid-infrared that are required to garner a complete picture of these low-luminosity dwarfs.